Conventionally, when manufacturing a semiconductor device, a flat panel display, or the like, a substrate such as a semiconductor wafer or a liquid crystal substrate is processed with a processing solution such as a cleaning solution.
In a substrate liquid processing apparatus for performing such a liquid process on the substrate, a two-fluid nozzle is used to spray droplets of the processing solution on a surface of the substrate.
The two-fluid nozzle has a circular hole-shaped liquid discharge portion for discharging the processing solution and a circular ring-shaped gas discharge opening for discharging a gas. The liquid discharge portion is formed at a central portion of a lower end portion of the two-fluid nozzle, and the gas discharge opening is formed at an outside of the liquid discharge portion. The two-fluid nozzle discharges a processing solution of a certain flow rate downward from the liquid discharge portion and also discharges a gas of a certain flow rate toward the processing solution from the gas discharge opening inwardly. The processing solution and the gas are mixed at an outside of (under) the two-fluid nozzle. The processing solution is dispersed due to a discharging pressure of the gas, so that the droplets of the processing solution are formed. Then, the droplets of the processing solution in a mist form are sprayed on the substrate (see, for example, Patent Document 1).
Patent Document 1: Japanese Patent Laid-open Publication No. 2004-356317
In the aforementioned conventional two-fluid nozzle, the droplets of the processing solution are formed by dispersing the processing solution discharged in a cylindrical shape from the circular hole-shaped liquid discharge portion at the central portion of the lower end portion of the two-fluid nozzle with the gas discharged from the gas discharge opening at the outside of the liquid discharge portion. However, in such a conventional two-fluid nozzle, the processing solution is not efficiently dispersed. As a result, droplets not having sufficiently small diameters may be formed. Further, the diameters of the formed droplets may become non-uniform. Thus, a liquid processing effect (for example, a cleaning effect) by the droplets of the processing solution may be deteriorated.